1. Field of the Invention
The present invention relates to a mechanism for enhancing power control in communication networks. In particular, the present invention is related to apparatuses, methods and computer program products providing a mechanism by means of which an improved power control in time division based communication networks, such as a local area time division duplex network is provided for enabling more flexible and efficient transmission power settings for communication network elements like UEs in the local area.
2. Related Background Art
Prior art which is related to this technical field can e.g. be found by the technical specification 3GPP TS 36.213, for example according to version 10.2.0.
The following meanings for the abbreviations used in this specification apply:    DL: downlink    DwPTS: downlink pilot time slot    eNB: evolved node B    E-UTRAN: evolved universal terrestrial radio access network    FDD: frequency division duplex    GP: guard period    LA: local area    LTE: Long Term Evolution    LTE-A: LTE Advanced    MCS: modulation and codeing scheme    PC: power control    PDCCH: physical downlink control channel    PRACH: physical random access channel    PRB: physical resource block    PUCCH: physical uplink control channel    PUSCH: Physical Uplink Shared Channel    RNTI: radio network temporary identifier    RRC: radio resource control    SF: subframe    SRS: sounding reference symbol    TDD: time division duplex    TPC: transmission power control    Tx: transmitter    UE: user equipment    UL: uplink    UpPTS: uplink pilot time slot    UTRAN: Universal Terrestrial Radio Access Network
In the last years, an increasing extension of communication networks, e.g. of wire based communication networks, such as the Integrated Services Digital Network (ISDN), DSL, or wireless communication networks, such as the cdma2000 (code division multiple access) system, cellular 3rd generation (3G) communication networks like the Universal Mobile Telecommunications System (UMTS), enhanced communication networks based e.g. on LTE, cellular 2nd generation (2G) communication networks like the Global System for Mobile communications (GSM), the General Packet Radio System (GPRS), the Enhanced Data Rates for Global Evolutions (EDGE), or other wireless communication system, such as the Wireless Local Area Network (WLAN), Bluetooth or Worldwide Interoperability for Microwave Access (WiMAX), took place all over the world. Various organizations, such as the 3rd Generation Partnership Project (3GPP), Telecoms & Internet converged Services & Protocols for Advanced Networks (TISPAN), the International Telecommunication Union (ITU), 3rd Generation Partnership Project 2 (3GPP2), Internet Engineering Task Force (IETF), the IEEE (Institute of Electrical and Electronics Engineers), the WiMAX Forum and the like are working on standards for telecommunication network and access environments. Examples for new communication technologies are for example LTE and LTE-A of 3GPP.
For example, in LTE represent is the next evolution of 3GPP based communication technology high data rates the DL and UL direction as well as reduced latency for packet transmissions is tried to be achieved. For this purpose, orthogonal frequency division multiple access (OFDMA) is the multiple access method used in the DL direction while in the UL direction single-carrier frequency division multiple access (SD-FDMA) mode is used. There are two different duplex modes for separating the transmission directions from the user to the base station and vice versa: on is frequency division duplex (FDD) and the other is time division duplex (TDD). In the case of FDD, the downlink and uplink are transmitted using different frequencies. In the TDD mode, the DL and UL are on the same frequency and the separation occurs in the time domain, so that each direction in a call is assigned to specific timeslots. The TDD mode is used for transmissions in unpaired frequency bands.
Both the uplink and downlink for LTE are divided into radio frames of a specific length (e.g. 10 ms). A frame consists of two “half-frames” of equal length, with each half-frame consisting of e.g. 10 slots, wherein two consecutive slots form one subframe. TDD may use the same frequency bands for the uplink and the downlink. The transmission directions are separated by carrying the UL and DL data in different subframes. The distribution of subframes between the transmission directions can be adapted to the data traffic and is done either symmetrically (equal number of DL and UL subframes) or asymmetrically.
Asymmetric distribution of subframes may be employed, for example, in LTE-A systems, such as TDD systems in a LA scenario (LA TDD). For example, the asymmetric resource allocation in LTE TDD is realized by providing seven different semi-statically configured uplink-downlink configurations defining a respective number and order of UL subframes and DL subframes in the transmission frame. Due to these different configurations, it is possible to provide between 40% and 90% DL subframes which allows a certain flexibility in the resource allocation in the LA TDD network.
For TDD deployments in general, interference between UL and DL including both basestation-to-basestation and UE-to-UE interference is typically handled by statically providing a guard period and adopting the same frame timing and uplink-downlink configuration practically in the entire network. However, in an LA network, the interference between UL and DL may occur again since it may be of interest to consider different UL/DL allocations in the neighboring cells. This is because a same DL/UL configuration in different neighboring cells of the LA network may not match the traffic situation in the different LA cells having generally a small number of users. However, in order to handle such an interference, it is necessary to conduct a suitable power control, so that this may have a heavy impact on the transmission power settings for a UE in the LA network.
Also the DL-UL interference in multi-cell scenarios is to be considered. As a result, an interference level between different subframes of the same frame may be significantly different.